Numerous approaches have been developed to protect flammable substrates from fire. One approach that has found widespread utility is the application of fire-retardant coatings to the substrate. Fire-protective coatings may be broadly classified as ceramic-based coatings, ablative coatings, intumescent coatings, and vapor-producing (sublimation) coatings, although in practice there may be substantial overlap of the chemical and physical fire-retarding mechanism between these approaches
Some conventional flame-retardant coatings employ so-called intumescent materials. These are materials that react in the presence of heat or flame to produce incombustible residues (“char”) which expand to a cellular foam having good insulation properties. Generally, intumescent materials comprise a carbonific material, typically a polyhydridic substance, such as a sugar or polyol, and an intumescent catalyst which is a dehydrating agent, such as phosphoric acid, usually introduced as a salt or ester. Upon heating, the acid is believed to catalyze the dehydration of the polyol to polyofefinic compounds which are subsequently converted to carbon char. “Blowing agents” which release nonflammable gases upon heating may be used to facilitate formation of the cellular foam.
Despite the effectiveness of intumescent coatings in protecting flammable substrates, there are certain disadvantages associated with their use. For example, the intumescent reaction can produce large bubbles in the coating which, upon rupture, may expose the underlying substrate. Such localized regions of exposed substrate are thereby rendered unprotected and may provide sites at which combustion of the substrate can occur.
Despite the advances in protective surface coatings, there remains a need for coatings which overcome some or all of these disadvantages.
It is accordingly an objective of the present invention to provide coatings which protect a substrate against heat or flame when used alone or in combination with one or more additional coating layers, including for example, intumescent coatings, fire-retardant coatings, and water-resistant coatings.
It is a further objective of the present invention to provide latex paints which protect a substrate against heat or flame.